Radiating member of sound-signaling apparatus



' June 22,1925.

' 1,589,962 H. HECHT :1- AL RADIATING [HUBER OF SOUND SIGNALING APPARATUS mm Jan. 6. 1921 4 4 Sheets-Sheet 1 June 22,1926. H 1,589,922

' 4H. HECHT ET AL- RADIA'IING MEMBER or sotmn SIGNALING APPARATUS Filed Jan. 6. 1921 4 SMMBESMM 2 mm... 2 & A- @-W I swa 1926;

H. HECHT 51' AL manna ususzn or SOUND smmuna minus Filed Jan. -s,, 1921 4 Sheets-sheaf a wm' Wu June 22,1926.

H. HECHT ET AL RADIATING MEMBER SOUND SIGNALING APPARATUS mm Jan. "a. 192i 4 sheets-sheet 4 I reach in a.

FATE-ill? HEIEQ'BIQE ELEGHT, OF KIEL, WALTER HAHNEMANN, OF PLON, AND WILHELM RU- DSLPE AND ALABD DU BOIS-REYMOND. GE KXTZEBEBG, HEAR KIEL, GERMANY, A$SEGN3R$ TO IRE FIRM SIQNAL GESELLSCEAFT M. ELK, OF EIEL, GERMANY.

nanm'rme MEMBER. or swan-SIG ALING 'arranarus.

applicetiiin filed January 6, 1821, Serial E0. 485,565, and in Germany June 14., 1915.

that vibrates in response to sound waves is used whose natural noteor rate of vibration is higher than the frequency at which it is to operate, i. e. higher than the fre-' 'quency that is to be employed for signaling, it will have to be of a certain thickness because, apart from-other factors that determine its dimensions, the natural tuning of such ratio of its diameter to its thickness. At

the relatively high frequencies or rates ot vibration eni loycd in submarine sound sig naling the tiickncss of such a diaphragm will be very considerable. If its natural frequency higher than the signaling frequency it is exceedingly difiicult to so excite it when sending that it executes motions of sutlicient amplitude, because this excitation has to be carried out by another vibratory member or structure that is coupled to the vibrating or radiating plate, and with the aid of which vibrations that correspond to the signaling frequency have to he produced in the entire apparatus, and it is a ditiicult matter to apply forces in an apparatus of this kind that are powerful enough to bend the thick diaphragm sufiiciently}. If the active parts of the system areexcited without any advantage being taken of any natural frequency i. e. if the parts merely execute motions which external forces compel them to carry out regardless of any kind of tuning, the said difficulty will be increased.

When diaphragms are employed that are tuned to the signaling frequency the said diiliculty, although it is reduced, still exwill! is that it exceedingly dillicult in any to accurately tune large diaphragms .nd to maintain their tuning in a practical installation, the more so because, as will be shown hereinafter, iisible to damp such diaphragm-s sulliciently,

or in other words the crest of the resonance If, in an apparatus of this kind, a plate plate is determined by thev 'water against which it abuts.

; and another obstacle to be contended is as a rule not poscurve of the diaphragm cannot be made broad enough. 1

If diaphragms or plates are used whbse natural frequency is considerably below the signaling frequency and if the attempt is made to excite 'them at the. signaling frequency the plate will, as-a rule,-execute a form of vibration that corresponds to thesignaling frequency i. e. the form of vibration of an harmonic. WV hen oscillating in this way the behaviour of the plate is often such that different partsof its surface move in opposite directions. This is a great drawback because it is most desirable that much as possible of the whole surface of the diaphragm shall operate to radiate energy into the water i. e., asmuch as possible of theentire area shall-operate simultaneously inpmduc-ing an increased pressure or a reduced pressure in the volume of If different parts of the surface oscillate in opposite directions the water will be enabled to move to and fro between these parts, i. c. it'

would be able' to escape from one part to another of the diaphragm without the desired changes of pressure bein produced in it. Hence a phenomenon arises similar to that knownin the science of electricity as a wattless current, he. a part of the But above all things there is one objection in particular, which is equally serious for senders and receivers, that forbids the use of thick i. e., highly tuned, plates. E10 pcrience has shown that with such platesit not possible to obtain a damping elfect, i. e., a breadth of the crest of the resonance curve of the plate, that is large enough for satisfactory useful damping and to render it possible to keep the signaling frequency (i. e. the rate of vibration used for signa .ing) within the limits between which a sufficiently high efficiency is obtained. To obtain the desired result stiffening-members are used, or the diaphragm is made thicker, at the parts where lllltl01..I B.bl6 nodal lines are likely to be formed in it. The essential difference between a. plate of. this kind and an ordinary plate of uniform thicknessconsists in the mass and elastic force of the former being unevenly distributed over its surface, and the idea that this distribution must be carried out in accordance with the form of the vibrations that the diaphragm is desired to execute is the fundamental idea underlying the present invention.

In the case of the fundamental form of vibration the simplest plan consists in pro- .viding stiffening rihs'on the diaphragm that extend in the di ction from its periphery towards its centre. -Radial blades stood on edge, .or.perpendicular to the surface of the diaphragm, may be used for this purpose.

They are preferably bevelled down towards the periphery and towards the middle of the diaphragm, and they are made of such length that they do not extend as far as the periphery and as far as the center of the diaphragm, so that zones at the peri hery and middle of the diaphragm are le. t nn ribbed. This is done in order to make the diaphragm flexible at these parts, these llexible parts being nece -sary to render a bulging of the diaphragm at all possible. \Vith this arrangement the vibratlng or exciting force is applied or taken from the centre of the diaphragm where a stitl'ened platelike zone is preferably left or produced. This zone may be smaller or larger in extent. If it is made very large a body will result allot whose points will .move parallel to each other and execute the same travel, i. e. a body that oscillates like a piston. Around this body there will then be an annular ribbed zone. e

- The rendering substantially rigid or stitfening of a certain zone or zones of the diaphragm may be :u- -on1plisl1e l by means of ribs or by increasing the thickness of the diaphragm at the said zone or zones.

The invention is shown in the drawing as applied to various constructional forms of sound signaling apparatus.

Fig. 1 represents a longitudinal section of a part of a sending and receiving apparatus whose diaphragm is provided with radial .ribs in'suc' 1 v manner as to cause it to execute vibrations of the desired form.

-l ig. 2 shows a front \'lt\V oi the diav phragm of Fig. 1.

Fig. 3 illustrates a constructional l'orm 0i? :1 similar type of apparatus in which the diaphragm is connected with another form of vibratory structure,

Fig. 4 shows the apparatus of Fig. 25 provided witha special kind of vibratory stru whic the middle portion of the diaphragm is stiffened by ring-shaped stiffening menr bers and interconnecting. radial stiffening members.

Fi 7 shows a form of plate or diaphragm in w ieh the stiffening eifeet'is'obtained by thickening the diaphragm instead of by individual ribs.

In Fig. 1, A is a casing, preferably cylindrical in shape, containing a sender equipment, and'arranged to be submerged. The electromagnetic exeiter is formed of an electromagnet B that is divided into two parts by an air gap. The two parts of the electromagnet B are rigidly fixed. to two masses C and C which in turn are connected to each other. by elastic rods 1), Dwhose aggregate cross-section is made such that the systemcomposed of the'parts C C*, D, D, B represents a vibratory structure or exeiter. that is tuned to the frequency to be employed in signaling.

The one end of the casing A is closed by the diaphragm E to the middle of which the mass C and hence the whole exciting device is fixed.

In accordance with the invention the free annular surface of the diaphragm between ,the edge of the casing A and the mass C t b f a much higher frequency than those by which the diaphragm is excited. Hence tie ribs suppress. the tendency of the diaphragm to form a no'dal line at or near the middle of the annular portion of its surface that is located. between its periphery and the mass (1. In other 'wordsthe ribs force the diaphragm to execute vibrations of .the form of its fundamental vibrations in spite of its being excited by an alternating force whose frequency is much higher than its fundamental note. v

An apparatus ofthis kind is equally applicable for the sending and receiving of sound waves. For sending urposes the alternating current winding of the magnet is connected, to a source of alternating cur rent and for receiving it is connected to a telephone receiver or some other form of an alternating ctu'rent detector.

The parts in Figs. 3 and 4 which correspond to these of Figs. 1 and 2 have similar an apparatus in two separate masses m co. But in Fig. 3 a tuning wit a microphone J is attached diaphra i (I; electric conductors passed through a stuffing box I:

and connected to the microphone.

In the arra geznent shown in Fig. 4 the vibratory structure F QlllplO":(l consists of and m connected to each other by an elastic rod S. Instead oia single rod plurality of the same may liccei ng .ericcs of the above-described hind on th advantage. that on account of the form of the vibrations executed by the t V well defined, is possible to make their tuning and damping uniform although their constructions may differ. The eiitire surface of the diaphragm yibretes in unison, and as its mass is small while its area is comparatively large, it can be damped in much higher degree than phi-agm.

"l 'antage gained by com- A part Dining :1 r1 shown in I? -which structure itself is not a part oi this invention-with a diaphragin constructed. in accordance with the invention is that it permits t t most important factors petining to the ribrations oi the apps: s for era 1 pic radiation and dam he calculated and fired beforehand.

The desired plished, elthor simply llllf'iifi} 'itl'ening may he accom- .io't so completely, by a the diaphragm at the places where .i stillness ii to be increased. A diaphragm ""ic.cd in this manner will, when by more. y forces, also produce greater acoustic 'ects than an ordinary diaphragm of 1 uniform thicitness. The diilcrencc between the two forms of: stiffening means (ribs and thickening) lies only in their eiiiciencies.

l obi in a form of vibration .dar as possible, a circular ,Cll'l genera is preferred. reason a diapurngm ot a difiepe. say a square diaphragm, is to A the abovie-mentioned means armonics may be immediis used, in the proper gore that is most apt to in former: i'iphragin when excited by the selected exciting means must then be sought, and the ribs are then applied so as to form bridges across the ll 'lal lines. In the case of a square diaphragm these ribs will have to extend radially in a circular dia 'ihrugm. Of course, in this too. the stiffening" may be accomplished by thickening the diaphragm.

in the device sl'uzwn in. Fig. 5; the diapEn-ugm pro ided with a comparatively rigid middle portion. lIlio 'ihrugms All); a middle portion that. is still'cned or strong enough to cause all its parts to move along parallel lines, and that is held by a marginal spring member, are known, but an important fact in connection therewith was overlooked and this is that this marginal spring portion or member, if it is simply made in the form of a thin portion of the plate, is bulged inwards by the pressure directed against the middle portion, while the middle portion is moving outwards and vice verse. To prevent this, in accordance with the invention, the marginal spring portion is stlllllletl with radial ribs, the arrangement of these ribs being such as to leave two only very narrow circular zones-un inner and an outer zone adjacent to the annular spring portion unstili'encd, each of the unstit'fened zones acting as a movable joint that extends along in circle. it is possible in this Way to compel all parts of the ring-shaped marginal spring portion to vibrate in phase with each other. In accordance with'the invention the stiff middle portion of the plate is made of such size or shupc that its fundamental-note is higher than the highest rate of vibration used for signaling. If this rate of vibration is high the middlepol'tion would have to be exceedingly thick and heavy. l-Ience it is udvuntz cons to stiffen this middle portion alm by ribs stood on edge. 111 this waya vibrating plate is formed which consists chiefly of a portion whose various parts all oscillate along parallel lines like the parts of a piston and upon whose remaining ring portion no harmful evasive motions occur at the frequency at which the diaphragm is operated. 13y proceeding along these lines it is possible to produce vibrating plates that oscillate in a certain well dctined manner and which in spite of this, have a much larger (liumctcr than such plates may have if their entire surface from the periphery to the centre is made so as to permit of its dill'erent portions moving in opposite directions.

lly placing the points at which the exciting, force is applied apart from each other as 'l'ar possible the uniformity of the form of the vibrations of the plate may be ensured in a still greater degree Fig. 5 shows a longitudinal section of a sender of the kind foreshadowed in the last two paragraphs,and Fig. ll is a section on the line J-2 of Fig.

Fixed at its margin to the [hinge of a ca ing A (only partly shown) in the ordinary way by means of screw bolts 1) is a vibrating metal plate J. i The annular portion Elietwccn e and 7' near the periphery is still'eucd by radial ribs F, F which are made of such size that the natural note of the annular area is much higher than the signaling i'rcqucncy. The middle portion Gr situated between the points' 6, e is also ribbed in ordcx' to obtain the greatest possible stillness with a. minimum of weight. But whereas the .one at 7'' near the margin and one at e ed jacent to the middle portion G, which not as movable joints-when the plate vibrates,

the middle portion is surrounded by a high peripheral 1'ib.K and is stiffened by radial ribs L in such a manner that it is, as a whole, as stiff aspossible.

In the constructional form shown the exciting device by which the plate is caused to vibrate consists of a tuning fork H whose prongs may be oscillated by an electromagnet (not shown). The stem of the fork is not directly attached to the middle of the central rigid portion of the plate but is connected to points near the periphery of this portion by the medium of a very stilt transverse beam or coupling plate T. By this means the exciting force is applied at points near to the circumference of the stitl middle portion G of the vibrating plate, so that these forces are distributed as uniforinlyas possible over the surface of the middle portlon. r

Thisarrangement may be used to equal advantage both in sound producers and receivers. Y

In F 7 a 15 a thick r1111 b which the ibrating plate is attached to a casing g or the like, I) is a thick middle portion and 0, c

a thick annular portion extending along a circle whose radius is about half that of the entire diaphragm. Between the thick annularportion 0 and the parts a" and b there are two thinner flexible parts or shown. The middle line in of the r be arched inwards, or outwards a? it may be straight. '20

We claim i l. A vibratory diaphragm for acoustic apparatus, provided with rigid and flexible zones arranged in radial symmetry, there being only two flexible zones,'these flexible 5 zones being ring-shaped, one to ing the outer boundary of the diaphragm sue the other being concentrically arranged within the first-named, a central rigid being, enclosed by the inner flexible zone, and 50 another rigid zone being enclosed between the two flexible zones.

A device according to claim 1, in which the rigidity of the two rigid zones is st, 1 by inearls of stiffening ribs,

3. A device according to c bined with :1 tuned vibrator tuched to the central rigid 4. A device according to cl the two flexible zones are e 5. A deviceaccording to cl the central rigid zone executes amplitudes of vibrations 6. A device ac'cordin to cla the two rigid zones vibrate in each other.

In testimony whereof we atiix our tures.

. HEINRICH HEC "ll.

WVALTER. HAHN; RIANEJ. IVILI-IELM RUDULPH. ALARD DU BQIS-RE YI-ZSFD, 

